Inductive position sensor

ABSTRACT

A resonant rotor, for use in an inductive position sensor, includes a rotor core, a first rotor coil, and a rotor capacitor. The first rotor coil includes a first twisted rotor loop drawn about the rotor core and the rotor capacitor is connected in series with the first rotor coil. For a second embodiment, the first rotor coil includes a second twisted rotor loop. The first rotor coil has a first symmetry and the inductive position sensor includes a stator. An excitation coil is drawn on the stator and has a second symmetry. The first symmetry substantially corresponds to the second symmetry. A method for determining a position of an object using an inductive position sensor includes generating three electromagnetic fields using respective excitation coils, inducing voltages, respectively, in three receive coils, and determining based on voltages a position of an object coupled to a resonant rotor. The voltages being based on mutual inductances arising between the rotor with each of the excitation and receive coils, and the elimination, by the resonant rotor, of mutual inductances arising between the excitation and receive coils.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to, as a divisional application, U.S.utility patent application Ser. No. 15/802,000, which was filed on Nov.2, 2017, and to U.S. provisional application No. 62/548,941, filed onAug. 22, 2017, both applications were filed in the name of inventorJacques Jean Bertin and are entitled “Inductive Position Sensor,” theentire contents of each application are incorporated herein byreference.

TECHNICAL FIELD

The technology described herein generally relates to devices, systems,and methods for determining the angular and/or linear position of anobject. More specifically, the technology described herein generallyrelates to electronic devices, systems, and methods which utilizeelectromagnetic principles, such as inductance, to determine an angularand/or linear position of an object.

BACKGROUND

Position sensing devices, including inductive position sensors, arewidely used today. Various uses include, but are not limited to,automobiles and other vehicles, factory settings, personal products, andotherwise. Inductive position sensors are often used to determine theposition of an object, such as brake pedal, a throttle, or otherwise,hereafter defined as a “target.” Today, inductive sensors typicallyinclude an excitation coil configured to generate an electromagneticfield when electrical current flows through the coil, a receiving coilconfigured to detect an electrical potential, a voltage, induced in thereceiving coil by the currents flowing through the excitation coil, anda rotor. The rotor is configured to disturb the amount of electricalpotential induced in the receiving coil based on the rotor's position.The rotor is typically attached, directly or indirectly, to the target,such that as a target's position changes, the rotor's relative positionalso changes. Such changes in the position of the rotor, in turn,uniquely disturb the voltages induced in the receiving coil such thatthe position of the rotor, and thereby the target, can be determinedbased on the changes in the electrical potential induced in thereceiving coil. In short, a rotor can be defined to affect the inductivecoupling between the excitation coil and the receiving coil bymathematical functions (each a “transfer function”). Circuitry isconnected to a receiving coil to detect and determine a rotor's relativeposition based on the relative amplitudes and changes thereof induced inthe receiving coil.

One example of a known inductive position sensor is described in U.S.Pat. No. 9,528,858, which issued on Dec. 27, 2016, in the name ofinventor Jacques Bertin, and entitled “Inductive Sensor,” the entirecontents of which are incorporated herein by reference.

More specifically, inductive position sensors often use a single-turnreceiving coil that is laid out in a rotational symmetry around one ormore single turn or multi-turn excitation coils, collectively, a“stator.” As shown for example in FIG. 1A, a stator 100 often includes afirst coil 101 that includes one or more first loops 101 a-101 n, and asecond coil 102, commonly having only a multi-turns single loop. Boththe first coil 101 and the second coil 102 are often drawn onto a singleor multiple layer PCB 104. Either of the first coil 101 or second coil102 may be respectively configured as excitation coils or receive coils.As shown, the first coil 101 commonly includes multiple loops 101 a-100n drawn across one or more layers of the PCB 104. FIG. 1B provides arepresentation of a bottom view of the PCB 106 where loops 100 a-110 nof the first coil 101 are drawn. The second coil 102 can be configuredin a clockwise or counter-clockwise pattern on the top or first layer, asecond layer, or using multiple layers of a multi-layer PCB 104.

As shown in FIG. 1C, a common embodiment of a rotor 108 typicallyincludes a rotor coil 110 with symmetry similar to the symmetry usedwith the first coil 101. The rotor coil 110 is often drawn such that itaffects the mutual inductances generated between the first coil 101 andthe second coil 102 as a function of the rotor's angular position Θ andin accordance with one or more transfer functions.

An electrical circuit 112 schematic representation of inductive positionsensor is shown in FIG. 1D. The circuit 112 includes three first coils101-1 to 101-3, functioning as excitation coils, where each coil has oneor more loops (not shown). The first coils 101-1 to 101-3 are typicallysymmetrical and are often respectively offset from each other by 120degrees, with each loop turning 90 degrees. The first coils 101-1 to101-3 are connected to an alternating current source (not shown) thatprovides an alternating current, in sequence, to each of the threecoils. Switching of each of the first coils 101-1 to 101-3 “on” and“off” is often accomplished using known devices, such as MOSFETtransistors and oscillators (not shown). The circuit 112 also includes asecond coil 102 functioning, as a receiving coil, connected to a signalprocessor (not shown). The signal processor is configured to detectchanges in the amplitude of a voltage potential induced in the secondcoil 102 by the first coils 101-1 to 101-3. Based on the amplitudesdetected and changes therein, the relative angular position of a rotor110 can be determined.

More specifically, an alternating current flowing through the firstcoils 101-1 to 101-3 generates first electromagnetic fields, which arerepresented by first field lines 114-1 to 114-3. The firstelectromagnetic fields are influenced by the position of the rotor coil110, such that the second coil 102 is induced to generate voltagepotentials based on second, modified electromagnetic fields 116-1 to116-3. The influence of the rotor 110 on the first electromagnetic field114 such that the receiving coil 102 senses the second electromagneticfields 116 is commonly defined as a rotor's “transfer function” that canbe represented mathematically.

While today's inductive position sensors are generally reliable, theyoften require too much printed circuit board (PCB) space when comparedto other components. For example, inductive position sensors today mayutilize 11 mm². In contrast, processors may utilize as little as 2-3mm². Today's inductive position sensor are also complex, requiring thedrawing of multiple precise loops to form the second coil 102. Drawingthe second coil requires additional PCB area hence additional cost. Withprocessor costs now approaching sensor costs, reductions in the formfactor and complexity of inductive position sensors are needed.

Further, electro-magnetic compliance requirements are becoming morestringent. Yet, with conventional inductive position sensors, stators100 often are susceptible to generating or receiving undesiredelectromagnetic emissions. For example, when the second coil 102 isconfigured as an excitation element, it will function as antenna andemit undesired electromagnetic waves. Contrarily, when the second coil102 is configured as a receiving element, it is often susceptible toexternal electromagnetic disturbances. Such disturbances may affect theaccuracy and sensitivity of the sensor.

Accordingly, a need exists for inductive position sensors that addressthese and other needs. Such needs are addressed by one or more of theembodiments of the present disclosure.

SUMMARY

The various embodiments of the present disclosure relate in general toinductive position sensors and systems and methods for manufacturing anduse thereof. In accordance with at least one embodiment of the presentdisclosure an inductive position sensor includes an excitation element.The excitation element may include a power source, a control circuit anda first excitation coil coupled to the power source. The firstexcitation coil may be configured to generate a first electromagneticfield. The inductive position sensor may include a second excitationcoil, coupled to the power source, and configured to generate a secondelectromagnetic field. The inductive position sensor may include a thirdexcitation coil, coupled to the power source, configured to generate athird electromagnetic field. The inductive position sensor may include acontrol circuit configured to control the flow of electrical currentsfrom the power source into and through one or more pairings of the firstexcitation coil, the second excitation coil and the third excitationcoil. The inductive position sensor may include a rotor configured to becoupled to each of the first electromagnetic field, the secondelectromagnetic field and the third electromagnetic field, based upon acurrent position of a target. The inductive position sensor may includea receive element. The receive element may include a signal processor.The inductive position sensor may include receive element having a firstreceive coil, coupled to the signal processor, configured for at leastone of the first electromagnetic field, the second electromagnetic fieldand the third electromagnetic field to induce a first voltage. Theinductive position sensor may include receive element having a secondreceive coil, coupled to the signal processor, configured for at leastone of the first electromagnetic field, the second electromagnetic fieldand the third electromagnetic field to induce a second voltage. Theinductive position sensor may include receive element having a thirdreceive coil, coupled to the signal processor, configured for at leastone of the first electromagnetic field, the second electromagnetic fieldand the third electromagnetic field to induce a third voltage. Theinductive position sensor may include a signal processor configured todetermine the current position of the rotor based on a received voltage,wherein the received voltage is a combination of at least one of thefirst voltage, the second voltage and the third voltage.

In accordance with at least one embodiment of the present disclosure aninductive position sensor may include first, second and third excitationcoils looped around a stator core. In accordance with at least oneembodiment of the present disclosure an inductive position sensor mayinclude first, second and third receive coils looped around the statorcore. For at least one embodiment, each of the first, second and thirdexcitation coils are connected to a common excitation node. For at leastone embodiment, each of the first, second and third receive coils areconnected to a common receive node,

In accordance with at least one embodiment of the present disclosure aninductive position sensor may include first, second and third excitationcoils are configured as a three-phase circuit. An inductive positionsensor may include first receive coil offset on the stator core from thefirst excitation coil; and each of a first receive coil, second receivecoil and a third receive coil may be configured as a three-phasecircuit. A corresponding excitation to rotor mutual inductance may existbetween each of the first, second and third excitation coils and therotor. A corresponding rotor to receive mutual inductance may existbetween each of the first, second and third receive coils and the rotor.The position of the rotor at a given time may result in a coupling ofthe corresponding excitation to rotor mutual inductance and the rotor toreceive mutual inductance. The coupling may be reflected in at least oneof the respective first voltage, second voltage and third voltage.

In accordance with at least one embodiment of the present disclosure aninductive position sensor may include a first excitation switch couplinga first excitation coil to a power source. An embodiment may include asecond excitation switch coupling a second excitation coil to the powersource. An embodiment may include a third switch coupling a thirdexcitation coil to the power source. A first receive switch may couple afirst receive coil to a signal processor. A second receive switch maycouple a second receive coil to the signal processor. A third receiveswitch may couple a third receive coil to the signal processor. Acontrol circuit may configure the first, second and third excitationswitches, at a first time, into a second anti-series configuration. Thesignal processor may be configured to receive the received voltage, anddetermine the position of the rotor, at the first time, as a function ofthe received voltage.

In accordance with at least one embodiment of the present disclosure foran inductive position sensor, the mutual inductances arising between theexcitation coils and rotor and between rotor and receive coils areapproximated by a sine waveform function of the rotor position. For atleast one embodiment, the received voltage is approximated by a sinewaveform function of twice the rotor position.

In accordance with at least one embodiment of the present disclosure foran inductive position sensor, a first excitation coil comprises at leastone set of first excitation loops, a second excitation coil comprises atleast one set of second excitation loops, and a third excitation coilcomprises at least one set of third excitation loops. For at least oneembodiment, the first, second and third excitation loops are drawn inseries on a stator core. The stator core may include a multi-layerprinted circuit board.

In accordance with at least one embodiment of the present disclosure foran inductive position sensor, a received voltage is proportional to amutual inductance arising at a given time between one of the first,second and third coils and the rotor for a primary-secondary pairing ofat least one of: the first receive coil and the second receive coil; thesecond receive coil and the first receive coil; the first receive coiland the third receive coil; the third receive coil and the first receivecoil; the second receive coil and the third receive coil; and the thirdreceive coil and the second receive coil. For at least one embodiment, arotor includes a rotor coil comprising a first rotor loop, a firstexcitation coil includes a first excitation loop, and the first rotorloop is symmetrical with the first excitation loop. For at least oneembodiment, the rotor includes a resonant rotor loop.

In accordance with at least one embodiment of the present disclosure, aresonant inductive position sensor may include a rotor, two or moreexcitation coils, inductively coupled to the rotor, two or more receivecoils, inductively coupled to each of the rotor and the two or moreexcitation coils, and configured to generate a received voltage, aresonance component connected to one of the two or more excitation coilsor t rotor, and an integrated circuit, wherein the integrated circuit isconfigured to determine the position of the rotor based on the two ormore received voltages. For at least one embodiment, the two or moreexcitation coils may be configured as twisted excitation loops about astator core. For at least one embodiment, the two or more receive coilsmay be configured as twisted receive loops about the stator core. For atleast one embodiment, the rotor may include a rotor coil having atwisted rotor loop. For at least one embodiment, one or more or each ofthe twisted excitation loops and the twisted receive loops may besymmetrical with the twisted rotor loop. For at least one embodiment,the twisted rotor loop may include a capacitor.

In accordance with at least one embodiment of the present disclosure, aresonant rotor for use in an inductive position sensor may include arotor core, a rotor coil, and a resonant component. For at least oneembodiment, the rotor coil may include at least one twisted rotor loopdrawn about the rotor core. For at least one embodiment, the resonantcomponent may be connected to the twisted loop to provideinductive-capacitive filtering for the resonant rotor. For at least oneembodiment, at least one twisted rotor loop may be symmetrical to atleast one of an excitation loop and a receive loop drawn about a statorcore of a stator. For at least one embodiment, a combination of a statorand a resonant rotor may be configured to provide a resonant inductiveposition sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, aspects, advantages, functions, modules, and components ofthe devices, systems and methods provided by the various embodiments ofthe present disclosure are further disclosed herein regarding at leastone of the following descriptions and accompanying drawing figures. Inthe appended figures, similar components or elements of the same typemay have the same reference number, such as 108, with an additionalalphabetic designator, such as 108 a, 108 n, etc., wherein thealphabetic designator indicates that the components bearing the samereference number, e.g., 108, share common properties and/orcharacteristics. Further, various views of a component may bedistinguished by a first reference label followed by a dash and a secondreference label, wherein the second reference label is used for purposesof this description to designate a view of the component. When only thefirst reference label is used in the specification, the description isapplicable to any of the similar components and/or views having the samefirst reference number irrespective of any additional alphabeticdesignators or second reference labels, if any.

FIG. 1A is a schematic representation of a top view of stator used inconjunction with one or more conventional inductive position sensors.

FIG. 1B is schematic representation of a bottom view of a stator used inconjunction with one or more conventional inductive position sensors.

FIG. 1C is schematic representation of a rotor as used in conjunctionwith one or more conventional inductive position sensors.

FIG. 1D is a schematic representation of an electrical circuit formed byone or more conventional inductive position sensors.

FIG. 2A is a schematic representation of a stator for use in aninductive position sensor and in accordance with at least one embodimentof the present disclosure.

FIG. 2B is a schematic representation of a stator into which are drawn afirst excitation coil “X1” and a first receive coil “R1” and inaccordance with at least one embodiment of the present disclosure.

FIG. 2C is a schematic representation of a stator into which are drawn afirst excitation coil “X1”, a second excitation coil “X2”, a firstreceive coil “R1” and a second receive coil “R2” and in accordance withat least one embodiment of the present disclosure.

FIG. 2D is a schematic representation of a stator into which are drawn afirst excitation coil “X1”, a second excitation coil “X2”, a thirdexcitation coil “X3”, a first receive coil “R1”, a second receive coil“R2”, and a third receive coil “R3” and in accordance with at least oneembodiment of the present disclosure.

FIG. 2E is a schematic representation of a rotor for use in an inductiveposition sensor and in accordance with at least one embodiment of thepresent disclosure.

FIG. 2F is a schematic representation of a rotor having a twisted loopdesign drawn on a multi-layer printed circuit board and in accordancewith at least one embodiment of the present disclosure.

FIG. 2G is a schematic representation of the mutual inductances arisingbetween the various components of an inductive position sensor and inaccordance with at least one embodiment of the present disclosure.

FIG. 3A is a schematic representation of an inductive position sensorhaving a resonant excitation circuit and in accordance with at least oneembodiment of the present disclosure.

FIG. 3B is a schematic representation of an inductive position sensorhaving a resonant receive circuit and in accordance with at least oneembodiment of the present disclosure.

FIG. 3C is a schematic representation of an inductive position sensorhaving a resonant rotor circuit and in accordance with at least oneembodiment of the present disclosure.

FIG. 3D is a schematic representation of a resonant rotor for use in aninductive position sensor having a resonant rotor circuit and inaccordance with at least one embodiment of the present disclosure.

FIG. 4A is a schematic representation of a first single-turn coil drawnon a rotor for use with an inductive position sensor and in accordancewith at least one embodiment of the present disclosure.

FIG. 4B is a schematic representation of a first coil and a second coildrawn in series on a multi-layer PCB rotor for use with an inductiveposition sensor and in accordance with at least one embodiment of thepresent disclosure.

FIG. 4C is a schematic representation of the second coil drawn at halfthe symmetry offset of the first coil on a multi-layer PCB rotor for usewith an inductive position sensor and in accordance with at least oneembodiment of the present disclosure.

FIG. 4D is a graph depicting the amplitude response profiles of each ofa symmetrical single coil rotor and a multi-coil rotor for use in aninductive position and in accordance with at least one embodiment of thepresent disclosure.

FIG. 4E is a graph depicting the harmonic response profiles of each of asymmetrical single coil rotor and a multi-coil rotor for use in aninductive position and in accordance with at least one embodiment of thepresent disclosure.

FIG. 5A is a straightened representation of the rotor coil for anangular sensor for use with an inductive position sensor and inaccordance with at least one embodiment of the present disclosure.

FIG. 5B is a schematic representation of the stator for an angularsensor of FIG. 5A as drawn onto a printed circuit board for use with aninductive position sensor and in accordance with at least one embodimentof the present disclosure.

FIG. 5C is a schematic representation of a resonant rotor as drawn ontoa printed circuit board for use with an inductive position sensor and inaccordance with at least one embodiment of the present disclosure.

FIG. 6 is a schematic representation of a use of an inductive positionsensor as a linear position sensor and in accordance with at least oneembodiment of the present disclosure.

DETAILED DESCRIPTION

The various embodiments described herein are directed to devices,systems, and methods for inductively determining the position of anobject. As shown in FIGS. 2A-2C, at least one embodiment of a stator foruse in an inductive position sensor of the present disclosure, includesa stator 200 having at least two excitation coils, as designated by X1and X2, and at least two receive coils, as designated by R1 and R2. Forat least one embodiment, a third excitation coil X3 and a third receivecoil R3 may be used (as further shown in FIG. 2D). Each of the two ormore excitation coils “X1-X3” and the two or more receive coils “R1-R3”are respectively offset by 120 degrees and include a twisted loop design202 a-n through a multi-layer stator core 208, as shown for a singlecoil and for purposes of illustration and explanation in FIG. 2A andFIG. 2B. A PCB may provide the stator core 208 for the coils used ingenerating electromagnetic fields when current is forced through thecoils. Each of the loops is commonly turned by 180 degrees relative toan immediately preceding loop. It is to be appreciated that theoffsetting nature of the twisted loop design 202 a-n minimizes thegeneration and reception of unintended electromagnetic fields and waves,such as the clockwise (right-hand) fields 204 a-d and thecounter-clockwise (left-hand) fields 206 a-d shown in FIG. 2A.Symmetrical loops may be used for each coil to minimize the evenharmonics of the sensor transfer function. Further, the third harmonicsof the sensor transfer function may be minimized when two of the coilsare connected in series. However, other offsets may be used for otherembodiments, with accordingly and computable changes in the transferfunctions by a person having ordinary skill in the art.

In FIGS. 2B-2D, a representation of one embodiment of a stator havingthree excitation coils and three receive coils is shown. Morespecifically, FIG. 2B shows a representation of a stator onto which hasbeen drawn a first excitation coil X1 and a first receive coil R1. FIG.2C shows the stator of FIG. 2C as additionally having drawn thereon asecond excitation coil X2 and a second receive coil R2. FIG. 2D showsthe stator of FIG. 2D with the addition of having drawn thereon a thirdexcitation coil X3 and a third receive coil R3. It is to be appreciatedthat any number of excitation and/or receive coils may be used inaccordance with an embodiment of the present disclosure. Further, it isto be appreciated that the drawing of the coils onto a PCB or othersubstrate may occur using any known processes. Such drawing may includethe drawing of any or all of the coils at any given process step and thepresent disclosure is not to be considered as being limited to asequential drawing of coils or otherwise. The coils may be drawn,deposited, or otherwise formed in a PCB or other substrate using anyknown or desired compounds, such as copper, aluminum, gold, or others.In accordance with at least one embodiment, each of the first, secondand third coils (both excitation and receive) are drawn on the PCB.

In FIG. 2E, a rotor 210 for use with at least the stator embodiment ofFIGS. 2A-2D is shown. The rotor 210 may be fabricated on a rotor core213 of any desired substance, such as a PCB or other substrate. Therotor 210 includes a conductive material that may be configured in acoil or any other conductive shape. The rotor 210 may be sized andconfigured to facilitate the detection of any desired range ofrotational and/or linear movements. The rotor 210 may include at leastone rotor coil 212. The rotor coil 212 may include a twisted loop design(as shown in FIG. 2E). As further shown in FIG. 2F where a multi-layerPCB or similar material is used for the rotor 210, the rotor coil 212may include two or more twisted loops 214 drawn between each of a toplayer and a bottom layer of the rotor core 213.

It is to be appreciated that by use of the stator 200 and rotor 210designs described above for at least one embodiment, whenever coils aredrawn, mutual inductances are generated between the respectiveexcitation coils and receive coils. When the two or more excitation andtwo or more receive coils are respectively configured using a commonexcitation node 216 and a common receive node 218, as shown in FIG. 2G,these mutual inductances are represented by: “M_x_(n)_r_(n)”(designating the inductance between excitation coil Xn and receive coilRn, where n is an integer); “M_x_(n)_rtr” (designating the inductancebetween excitation coil Xn and the rotor “rtr”; and M_rtr_r_(n)(designating the inductance between the rotor and receiving coil Rn. Forat least one embodiment, M_x_(n)_rtr and M_rtr_r_(n) have the samemagnitudes. For at least one embodiment, M_x_(n)_r_(n) is much smallerthan M_x_(n)_rtr and M_rtr_r_(n) and each of M_x_(n)_rtr, M_rtr_r_(n),and M_x_(n)_r_(n) are greater than zero. For at least one embodiment,M_x_(n)_r_(n) is minimized. For at least one embodiment, the amplitudesof M_x_(n)_rtr and M_rtr_r_(n) are maximized. It is to be appreciatedthat depending on the position of the rotor some mutual inductances maybe zero or negative.

As shown in FIGS. 3A-3C, an integrated circuit 310 for use in at leastone embodiment includes a control circuit, not shown, configured tocontrol the operation of excitation switches 308 _(X1)-308 _(X3) andreceive switches 308 _(R1)-308 _(R3). The excitation switches 308_(X1)-308 _(X3) connect a corresponding excitation coil to analternating current source 314. The receive switches 308 _(R1)-308 _(R)connect a corresponding receive coil to the signal processor 312.

In accordance with at least one embodiment of the present disclosure, aninductive position sensor may be configured to include three excitationcoils X1-X3, where a first excitation coil X1 is offset by 120 degreesrespectively from each of a second excitation coil X2 and a thirdexcitation coil X3. Such a configuration may be expressed mathematicallyin terms of the mutual inductances created between a given excitationcoil and the rotor as a set of transfer functions, as shown by EquationSet 1 below, where “x” is the rotor's angular position.Mx1_rtr=F(x)Mx2_rtr=F(x+120)Mx3_rtr=F(x+240)  Equation Set 1

Further, an inductive position sensor may be configured in accordancewith at least one embodiment of the present disclosure to include threereceive coils R1-R3, where a first receive coil R1 is offset by 90degrees from a corresponding first excitation coil X1, and the firstreceive coil R1 is offset 120 degrees respectively from each of a secondreceive coil R2 and a third receive coil R3. Such a configuration may beexpressed mathematically in terms of the mutual inductances createdbetween a given receive coil and the rotor as a set of transferfunctions, as shown by Equation Set 2 below, where “x” is the rotor'sangular position.M _(R1)_rtr=F(x+90)M _(R2)_rtr=F(x+210)M _(R3)_rtr=F(x+330)  Equation Set 2

It is to be appreciated, the using a Fourier series, F(x) can beapproximated. By use of twisted loop in the rotor, a constant term inthe Fourier series is zero. Further, due to the symmetry of the coils(both excitation and receive) the even harmonics in the Fourier seriesare minimized. Further, the fifth and higher harmonics in the Fourierseries may be neglected. Accordingly, the excitation coil X1-X3 to rotorinductances may be approximated by use of the Fourier series shown inEquation Set 3, and the receive coil to rotor inductances may beapproximated by use of the Fourier series shown in Equation Set 4, whereA1 is the fundamental amplitude and A3 is the amplitude of the thirdharmonic.M _(X1)_rtr=A ₁ sin(x)+A ₃ sin(3x)M _(X2)_rtr=A ₁ sin(x+120)+A ₃ sin(3x+360)M _(X3)_rtr=A ₁ sin(x+240)+A ₃ sin(3x+720)  Equation Set 3M _(R1)_rtr=A ₁ sin(x+90)+A ₃ sin(3x+270)M _(R2)_rtr=A ₁ sin(x+210)+A ₃ sin(3x+630)M _(R3)_rtr=A ₁ sin(x+330)+A ₃ sin(3x+990)  Equation Set 4

Further, it is to be appreciated that as the three combinations ofcoils, X1R1, X2R2 and X3R3, are induced, a three-phase signal isreceived by the receiving coils R1-R3 and provided to a signal processorconfigured to calculate the position “X” of the rotor at that time.Further, due to the 3-phases of the coil design the third harmonics canbe removed such that the received signal R(x) is proportional to twicethe cosine of the position of the rotor “x”, as shown by Equation Set 5.An AC excitation current is forced through the coils X1 and X2 inanti-series (the current flows from the integrated circuit 310 to X1,reaches the common node and returns to the integrated circuit 310through X2 but in opposite direction, as expressed by Xi-j (where “i”identifies a “primary” or forward path coil and “j” identifies a“secondary” or return-path coil) as expressed by the negative (“−”) signin Equation 5. It is to be appreciated that the “i—primary” and the“j—secondary” designators are used herein for purposes of identificationof coil pairings. The induced voltage across the coils R1 and R2 ismeasured with the two coils R1 and R2 being in anti-series, as expressedby Ri-j and the second negative (“−”) sign in Equation 5. The inducedvoltage, the received voltage, is proportional to the mutual inductancesbetween the excitation coils to rotor and the rotor to receiver coils,as expressed by the multiply (“*”) sign in the Equation 5. Similarly,R_(2_3)(x) and R₃₋₁(x) (or R₃₋₂ or R₁₋₃ or R₂₋₁) may be computed. For atleast one embodiment, the excitations can occur sequentially to measureat least two R_(i-j)(x) to calculate the position “x”. For at least oneembodiment, the received voltage may be calculated as a fixedcombination, a changing over time combination, a multiplexing orotherwise of one or more of the R_(i-j)(x) positions. For at least oneembodiment, parallel excitation of all excitation coils may be used,provided the relative amplitude of the excitation currents is known suchthat x can be extracted from the measurements of R_(i-j).

                                    Equation  Set  5R¹ ⁻ ²(x) = [{A₁sin (x) + A₃sin (3x)} − {A₁sin (x + 120) + A₃sin (3x + 360)}] *   [{A₁sin (x + 90) + A₃sin (3x + 270)} − {A₁sin (x + 210) + A₃sin (3x + 630)}] = [A 1 sin (x) − A 1sin (x + 120)] *   [A 1sin (x + 90) − A 1sin (x + 210)] = −1.5A₁²cos (2x + 210)R² ⁻ ³(x) = [{A₁sin (x + 120) + A₃sin (3x + 360)} − {A₁sin (x + 240) + A₃sin (3x + 720)}] *   [{A₁sin (x + 210) + A₃sin (3x + 630)} − {A₁sin (x + 330) + A₃sin (3x + 990)}] =   [A 1 sin (x + 120) − A 1sin (x + 240)] * [A 1sin (x + 210) − A 1sin (x + 330)] = −1.5A₁²cos (2x + 270)R³ ⁻ ¹(x) = [{A₁sin (x + 240) + A₃sin (3x + 720)} − {A₁sin (x) + A₃sin (3x)}] *   [{A₁sin (x + 330) + A₃sin (3x + 990)} − {A₁sin (x + 90) + A₃sin (3x + 270)}] =   [A 1 sin (x + 240) − A 1sin (x)] *   [A 1sin (x + 330) − A 1sin (x + 90)] = −1.5A₁²cos (2x + 150)

As shown by Equation Set 5, it is to be appreciated that the receivedvoltage(s) can be approximated by a sine waveform function of the rotorposition. For at least one embodiment, the approximation is a functionof twice the rotor position. It is to be appreciated that the receivedvoltage signal is often in the range of 0.1 to 10 millivolts. Such lowvoltages can be susceptible to interference. In accordance with at leastone embodiment of the present disclosure, a resonant inductive positionsensor is disclosed. A resonant inductive position sensor may include aresonant excitation circuit 300 having a capacitor C1 electricallyconnected to one or more of the excitation coils X1-X3 as shown in FIG.3A, a resonant receive circuit 302 having a capacitor C2 electricallyconnected to one or more of the receive coils R1-R3 as shown in FIG. 3B,or a resonant rotor circuit 304 having a capacitor C3 electricallyconnected in parallel to the rotor coil 212 as shown in FIGS. 3C and 3D.The capacitance for capacitors C1, C2 and C3 may be selected in view ofknown resonant (LC) circuit principles. It is to be appreciated that forat least one embodiment, by using a resonant circuit for one of thecoils, the received signal may be more than ten time (10×) larger thanthe signal received when a non-resonant circuit is utilized. Further, itis to be appreciated that a resonant rotor circuit 304 may be used toaddress mutual inductance concerns that may arise when the traces/loopsfor the excitation coils X1-X3 and the traces/loops for the receivecoils R1-R3 may be in close proximity, such as when such traces aredrawn on a common PCB and/or interfaced with a common integratedcircuit. These mutual inductances may disturb the received signal, astransferred via the rotor, by introducing signals that are independentof the rotor's position. Given that the received voltages arising due toany mutual inductance between the excitation and receive coils willoften be in quadrature, while the received voltages arising from theresonant rotor will be in phase. It is to be appreciated that thereceived voltages will commonly be in phase when a resonant rotor isused, and the excitation frequency is not far from the resonance of thereceived voltage arising from the rotor. Otherwise, the received voltagemay be in quadrature and superposed on the received voltage comingdirectly from the excitation. Further, for at least one embodiment, theresonant rotor circuit 304 can provide the enhanced signal strengthsachievable using a resonant circuit, while eliminating any disturbancescaused due to mutual inductance between the excitation and receive coilsby removing the quadrature signal, for example, by use of a synchronousrectifier. Accordingly, it is to be appreciated that for at least oneembodiment of the present disclosure a resonant rotor may be used.

Further, it is to be appreciated however, that the mutual inductancesgenerated may not be ideal, especially when the rotor 210 is in closeproximity to the stator 200 and a maximum amplitude (of A₁) results orwhen the PCB 208 is small. These concerns can be addressed in accordancewith at least one embodiment of the present disclosure by using amulti-coil rotor 400 having at least two coils 402 a-c. For at least oneembodiment, the multi-coil rotor 400 may include a capacitor (not shown)to provide the benefits of a resonant rotor circuit. As shown in FIG.4A, a first rotor coil 402 a may be drawn on a substrate 404. As furthershown in FIG. 4B, a second rotor coil 402 b may be drawn on thesubstrate 404. For at least one embodiment, the coils 402 a-402 b mayinclude a twisted loop design. The twisted loop design may have anynumber of loops, such as loops 402 a 1-402 a 4. For at least oneembodiment, the loops 402 a 1-402 a 4 may be drawn symmetrically. For atleast one embodiment, the loops 402 a 1-402 a 4 may be offset by 90degrees relative to a next loop. For at least one embodiment, the loops402 a 1-402 a 4 may be drawn across a single layer or a multi-layersubstrate 404, such as a single or multi-layer PCB. For at least oneembodiment, the symmetry of the rotor matches the symmetry of acorresponding stator. A plurality of rotor coil loops may be used toform multiple coils connected on one or more layers of a PCB. It is tobe appreciated, that many coils may exist over the rotor, and for atleast one embodiment, a rotation of the coils by half the rotationalsymmetry will result in an alignment of a second set of loops 402 b thatmatch a first set of loops 402 a, as shown in FIG. 4C (where a slightlyless than half rotation is used to show substantial alignment of the twoloops 402 a and 402 b).

As shown in FIGS. 4D and 4E, for at least one embodiment of the presentdisclosure improved performance may be realized by a multi-coil rotor400 versus a single coil rotor 200. More specifically, in FIGS. 4D and4E, signal measurements for a multi-coil rotor are shown over a 45degrees range. As shown, the expected signal period arises over the 45degrees range, when the multi-coil rotational symmetry is 90 degrees.

As shown in FIG. SA, the process of forming a sensor according to atleast one embodiment of the present disclosure may include theoperations of forming a straight sensor 500 and then bending the sensor500 into a circle to form a rotary sensor. It is to be appreciated thatthe capacitor “cap” shown may be replaced by a short.

In FIG. 5B, a layout of an inductive sensor 502 in accordance with atleast one embodiment of the present disclosure is shown asinterconnected on an PCB using nodes 504 a-504 n. It is to beappreciated that when multiple excitation coils and multiple receivecoils are used, an opening or “cut” somewhere to the coil is used tofacilitate interconnection of the coils to each of a common node and tothe integrated circuit.

In FIG. 5C, the layout of a resonant rotor 306 in accordance with atleast one embodiment of the present disclosure is shown. Like thestator, the resonant rotor layout may be substantially the same with theaddition of capacitor C3.

In FIG. 6, an embodiment of a linear position sensor 600 is shown inaccordance with at least one embodiment of the present disclosure. Asshown for a single twisted loop rotor configuration moving above astator coil having a twisted two or more loop configuration, a mutualinductance will arise. The principles of operation of the linearposition sensor 600 are substantially the same as those of therotational position sensor embodiments discussed above with a notedexception being that a signal processor (not shown) connected to thelinear position sensor 600 may be configured to convert an angulardisplacement of the linear rotor 602 into a linear displacement insteadof an angular displacement. For example, a movement of the linear rotor602 by one (1) inch across a linear stator 604 may result in a movementof the rotor relative to the stator, as sensed by the linear positionsensor of one (1) degree. It is to be appreciated that for at least oneembodiment the sensed angle of deflection is proportional to the lineardisplacement of the target. As further shown in FIG. 6, the relativeamplitude of the mutual inductances generated between the rotor and oneor more receive coils in the linear stator 604 may form a sinusoidalform, where a movement of the rotor by the same period will result in amaximum coupling of the linear rotor to the linear stator when a middleof the linear rotor is aligned with a middle of one or more loops of thelinear stator. Further, it is to be appreciated that for at least oneembodiment, the linear position sensor 600 may include use of amulti-excitation coil and/or a multi-receive coil configuration, asdiscussed above with respect to other embodiments of the presentdisclosure. Further, the linear position sensor 600 may include use of alinear rotor 602 having one or more rotor coils drawn thereon. Thelinear rotor 602 may include a capacitor, such as capacitor C3, toprovide a resonant linear rotor. A capacitor may alternatively be usedto provide a resonant linear excitation circuit or a resonant linearreceive circuit.

Accordingly, various embodiments of an inductive position sensor aredescribed. One or more of such embodiments may be configured for use asa rotational or a linear position sensor. Various embodiments mayinclude the use of multiple receive coils drawn onto a substrateproximate to corresponding excitation coils. Various embodiments mayinclude the use of resonant circuits, such as a resonant excitationcircuit, a resonant receive circuit and a resonant rotor circuit.Various embodiments may include the use of rotors having multiple rotorcoils. Further, methods of manufacturing of one or more embodiments ofthe inductive position sensor may be used in accordance with knownand/or future arising manufacturing principles and materials. Further,use of an inductive position sensor according to an embodiment of thepresent disclosure may arise in conjunction with any known or futurearising targets.

Although various embodiments of the claimed invention have beendescribed above with a certain degree of particularity, or withreference to one or more individual embodiments, those skilled in theart could make numerous alterations to the disclosed embodiments withoutdeparting from the spirit or scope of the claimed invention. The use ofthe terms “about”, “approximately” or “substantially” means that a valueof an element has a parameter that is expected to be close to a statedvalue or position. However, as is well known in the art, there may beminor variations that prevent the values from being exactly as stated.Accordingly, anticipated variances, such as 10% differences, arereasonable variances that a person having ordinary skill in the artwould expect and know are acceptable relative to a stated or ideal goalfor one or more embodiments of the present disclosure. It is also to beappreciated that the terms “top” and “bottom”, “left” and “right”, “up”or “down”, “first”, “second”, “before”, “after”, and other similar termsare used for description and ease of reference purposes only and are notintended to be limiting to any orientation or configuration of anyelements or sequences of operations for the various embodiments of thepresent disclosure. Further, the terms “and” and “or” are not intendedto be used in a limiting or expansive nature and cover any possiblerange of combinations of elements and operations of an embodiment of thepresent disclosure. Other embodiments are therefore contemplated. It isintended that all matter contained in the above description and shown inthe accompanying drawings shall be interpreted as illustrative only ofembodiments and not limiting. Changes in detail or structure may be madewithout departing from the basic elements of the invention as defined inthe following claims.

What is claimed is:
 1. A resonant rotor, for use in an inductiveposition sensor, comprising: a printed circuit board (PCB) comprising: arotor core; a first rotor coil; and a rotor capacitor; wherein the firstrotor coil includes a first twisted rotor loop; and wherein the rotorcapacitor is connected in parallel with the first rotor coil on the PCB;and wherein the resonant rotor induces signals in each of two or morereceive coils interconnected using one at least one of a common receivenode and a three-phase circuit.
 2. The resonant rotor of claim 1,wherein the first twisted rotor loop includes a full 360-degreemechanical turn.
 3. The resonant rotor of claim 1, wherein the firstrotor coil includes a second twisted rotor loop.
 4. The resonant rotorof claim 3, wherein the first twisted rotor loop is drawn symmetricallyrelative to the second twisted rotor loop.
 5. The resonant rotor ofclaim 1, comprising: a second twisted rotor loop off offset by ninetydegrees relative to the first twisted rotor loop.
 6. The resonant rotorof claim 3, wherein the second twisted rotor loop is rotated, relativeto the first twisted rotor loop, by half a rotational symmetry of thefirst twisted rotor loop.
 7. The resonant rotor of claim 1, wherein thefirst rotor coil has a first symmetry; wherein the inductive positionsensor includes a stator; wherein an excitation coil is drawn on thestator and has a second symmetry; and wherein the first symmetrysubstantially corresponds to the second symmetry.
 8. The resonant rotorof claim 1, wherein the rotor core is a single layer substrate.
 9. Aresonant rotor comprising: a printed circuit board (PCB) comprising: arotor core; a first rotor coil; and a rotor capacitor; wherein the firstrotor coil includes a first twisted rotor loop; and wherein the rotorcapacitor is connected in parallel with the first rotor coil on the PCB;wherein the resonant rotor is configured for use with an inductiveposition sensor; wherein the inductive position sensor comprises: anexcitation element comprising: a power source; a control circuit; afirst excitation coil, coupled to the power source, configured togenerate a first electromagnetic field; a second excitation coil,coupled to the power source, configured to generate a secondelectromagnetic field; a third excitation coil, coupled to the powersource, configured to generate a third electromagnetic field; whereinthe control circuit controls a flow of electrical currents from thepower source into and through one or more pairings of the firstexcitation coil, the second excitation coil and the third excitationcoil; a receive element, comprising: a signal processor; a first receivecoil, coupled to the signal processor, configured for at least one ofthe first electromagnetic field, the second electromagnetic field andthe third electromagnetic field to induce a first voltage; and a secondreceive coil, coupled to the signal processor, configured for at leastone of the first electromagnetic field, the second electromagnetic fieldand the third electromagnetic field to induce a second voltage; a thirdreceive coil, coupled to the signal processor, configured for at leastone of the first electromagnetic field, the second electromagnetic fieldand the third electromagnetic field to induce a third voltage; whereinthe resonant rotor, based upon a current position of a target, isconfigured for coupling with each of the first electromagnetic field,the second electromagnetic field and the third electromagnetic field;and wherein the signal processor determines the current position of anobject coupled to the resonant rotor based on a received voltage,wherein the received voltage is a combination of at least one of thefirst voltage, the second voltage and the third voltage.
 10. Theresonant rotor of claim 9, wherein each of the first excitation coil,the second excitation coil and the third excitation coil and each of thefirst receive coil, the second receive coil and the third receive coilare looped around a stator core; and wherein each of the firstexcitation coil, the second excitation coil and the third excitationcoil are connected in an excitation coil configuration comprising one ofa common excitation node and a three-phase circuit.
 11. The resonantrotor of claim 9, wherein each of the first receive coil, the secondreceive coil and the third receive coil are connected in a receive coilconfiguration comprising one of a common receive node and a three-phasecircuit.
 12. The resonant rotor of claim 9, wherein the control circuitselectively provides electrical power to each of the first excitationcoil, the second excitation coil and the third excitation coil in ananti-series configuration; and wherein the control circuit selectivelyconnects the signal processor to each of the first receive coil, thesecond receive coil and the third receive coil in the anti-seriesconfiguration.
 13. The resonant rotor of claim 1, wherein the inductiveposition sensor comprises two or more excitation coils; wherein a firstset of mutual inductance arises between the two or more excitation coilsand the rotor; and wherein a second set of mutual inductances arisebetween the two or more receive coils and the rotor; and wherein each ofthe first set of mutual inductances and the second set of mutualinductances are approximated by sine waveform functions of the rotorposition.
 14. The resonant rotor of claim 13, wherein a third set ofmutual inductances arise between the two or more excitation coils andthe two or more receive coils; wherein the third set of mutualinductances generate a quadrature signal in a received voltage providedby the two or more receive coils; and wherein the first capacitoreliminates the quadrature signal.
 15. The resonant rotor of claim 9,wherein a corresponding excitation to rotor mutual inductance existsbetween each of the first excitation coil, the second excitation coiland the third excitation coil and the rotor; wherein a correspondingrotor to receive mutual inductance exists between each of the firstreceive coil, the second receive coil and the third receive coil and therotor; wherein the position of the rotor at a given time results in acoupling of the corresponding excitation to rotor mutual inductance andthe rotor to receive mutual inductance; and wherein the coupling isreflected in at least one of the first voltage, second voltage and thirdvoltage.
 16. A method for determining a position of an object using aninductive position sensor comprising: generating a first electromagneticfield using a first excitation coil; generating a second electromagneticfield using a second excitation coil; generating a third electromagneticfield using a third excitation coil; inducing a first voltage in a firstreceive coil; inducing a second voltage in a second receive coil;inducing a third voltage in a third receive coil; determining based onthe first voltage, the second voltage and the third voltage a positionof an object coupled to a resonant rotor; wherein the resonant rotor iscoupled to each of the first electromagnetic field, the secondelectromagnetic field and the third electromagnetic field; wherein acorresponding rotor to receive coil mutual inductance arises between theresonant rotor and each of the first receive coil, the second receivecoil and the third receive coil; wherein a change in the position of theobject changes each of the corresponding rotor to receive coil mutualinductances and thereby the first voltage, second voltage and thirdvoltage induced in the respective first receive coil, second receivecoil and third receive coil; and wherein the resonant rotorsubstantially eliminates any mutual inductances arising between one ormore of the first excitation coil, the second excitation coil and thethird excitation coil with one or more of the first receive coil, thesecond receive coil and the third receive coil.
 17. A resonant inductiveposition sensor comprising: a resonant rotor; two or more excitationcoils, each uniquely inductively coupled to the resonant rotor; and twoor more receive coils, each second uniquely inductively coupled to theresonant rotor; wherein the resonant rotor has a first symmetry; whereinthe two or more excitation coils have a second symmetry; wherein the twoor more receive coils have a third symmetry; and wherein at least one ofthe first symmetry and the second symmetry is substantially identical tothe third symmetry; a signal processor configured to determine aposition of an object coupled to the resonant rotor based upon voltagesinduced in each of the two or more receive coils; wherein the voltagesare induced based upon a first set of mutual inductances arising betweenthe two or more excitation coils and the resonant rotor and a second setof mutual inductances arising between the resonant rotor and the two ormore receive coils; and wherein the resonant rotor includes at least onerotor coil having a twisted loop design and a capacitive elementconfigured to substantially eliminate, from voltages induced in the twoor more receive coils, a third set of mutual inductances arising betweenthe two or more excitation coils and the two or more receive coils. 18.The resonant inductive position sensor of claim 17, wherein each of thetwo or more excitation coils are drawn as first twisted loops about astator core; wherein each of the two or more receive coils are drawn assecond twisted loops about the stator core; wherein the resonant rotorcomprises at least one rotor coil drawn as a twisted rotor loop about arotor core; and wherein at least one of a first symmetry for the firsttwisted loops and a second symmetry for the second twisted loopssubstantially matches a third symmetry for the twisted rotor loops.